Reinforced propeller blade



Dec. 30, 1947.l J. H. MGKEE REINFORCED PROPELLER BLADE Filed Jan. 29, 1944 2 Sheets-Sheetl l INVENTOR Dec. 30, 1947.

J. H. MCKEE REINFORCED PROPELLER BLADE Filed Jan. 29, 1944 2 sheets-sheet 2 xNvENToR .f/nes H. McKee ATTORNEY n NNN Patented Dec. 30, 1947 REINFORCED PROPELLER BLADE James H. McKee, North Caldwell, N. J., assigner to Curtiss-Wright Corporation, a corporation of Delaware Application January 29, 1944, Serial No. 520,350

This invention relates to a hollow aircraft propeller blade which is provided with a novel reinforcing arrangement.

The invention has particular reference to a hollow propeller blade formed from plates disposed in facing relation and forming an interior chamber, each plate having a longitudinally extending rib formed integral therewith, the ribs facing each other throughout at least a part of the length thereof.

The invention has further reference to a propeller blade as herein described wherein a wedgeshaped connecting member bridges the space between and is connected to the aforesaid ribs.

Various other objects, advantages and features of my invention will become apparent from the following detailed description.

The invention resides in the reinforced hollow 4 Claims. (Cl, 170-159) propeller blade, combinations and arrangements of the character hereinafter described and claimed.

For an understanding of the invention andfor an illustration of one of the forms thereof, reference is to be had to the accompanying drawings, in which:

Figure 1 is a plan view of the camber plate section of a hollow propeller blade with a slotted rib formed on one face thereof;

' Fig. 2 is a plan view of the underside of the thrust plate section of a hollow propeller blade and illustrating an open bevelled slot formed therein;

Fig. 3 is a longitudinal sectional View taken on the line 3-3 of Fig. 1;

Fig. 4.is a longitudinal sectional view taken on the line 4-4 of Fig. 2;

Fig. 5 is a fragmentary longitudinal sectional view of the camber and thrust plates in assembled relation with a reinforcing wedge-shaped member therebetween;

Fig. 6 is a transverse sectional view taken on the line 6-6 of Fig. 5;

Fig. 7 is a fragmentary view similar to Fig. 6;

Fig. 8 is a fragmentary view similar to Fig. '7 illustrating the invention as applied to both of the propeller forming plates; and

Fig. 9 is a perspective View of the wedge-shaped rib connecting member per se.

Referring to Figs. 1 through 4, there is shown a metallic camber plate C and a complementary thrust plate T of the general character known ln the art for forming a hollow propeller blade B.

As illustrated, the camber plate C comprises a tubular shank III having extended therefrom, the camber plate II proper which generally, is of convex configuration, the convexity decreasing in a progressive manner as the tip end of the plate is approached whereby said camber plate C defines a, shallow opening of generally elliptical coniiguration. The thrust plate T comprises a plate proper I2 which generally is of ellipticalconguration corresponding with the aforesaid shallow opening of the camber plate C and, to less extent than the latter, it has convex shape. As will be observed in Fig. 2, the thrust plate T does not include a shank end portion as does the camber plate C.

As illustrated, the plates C and T include the respective longitudinally extending integral ribs I3 and I4 which, when said plates are associated one with the other in assembled relation, are disposed substantially in spaced, facing relation or in a common plane. In the form of the invention herein shown, although not necessarily, the ribs I3 and I4 are formed, as described in the pending application of James H. McKee, -Serial No. 493,314, led July 2, 1943, now Patent Number 2,431,411, issued November 25, 1947, by subjecting uniformly thick plane sheets of metal stock, to two or more milling machine operations whereby each sheet of metal is longitudinally tapered in such manner that the thickness of each sheet of metal decreases longitudinally therealong toward the tip of the blade. The milling cutter is so constituted that, while the tapering operation proceeds, a longitudinal strip of the original sheet of metal remains intact and forms the aforesaid rib I3 or I4, the ends thereof toward the left terminating approximately at the respective locations A, Figs. l, 2, 3 and 4. As a result of the described milling operations, the thickness or height of each of the ribs I3 and I4 increases progressively in a direction extending longitudinally along the propeller blade toward the tip thereof. Further, it is desirable that the milling cutter be so shaped that the described operation causes each of the ribs I3 and I4 to be bordered by fillets f as shown.

The ribs I3 and I4 thus formed on the camber and thrust plates C and T respectively, are subsequently subjected to a milling operation whereby a .closed slot or channel I5 is formed in the rib I3, and an open slot I6 similarly formed in the rib I4. The closed slot I5 terminates short of the right-hand end of the rib I3, as does the open slot I6 with respect to the rib I4. The slot I6 extends through the rib I4 and the thrust plate T with its exterior marginal edges bevelled as clearly shown in'Figs. 6 and 7. The closed slot I5, formed in the camber plate rib I3, is pro- 3 vided for the key-way like reception of one marginal edge portion of the tapered gusset or wedgeshaped connecting member indicated at I1 whereby a tongue-and-groove joint is formed which serves to more accurately locate the aforesaid connecting member I1 with respect to the aforesaid open slot I6, and thus assure accurate alinement of the wedge member I] with the slot I6 when thethrust'platefl'is secured to the camber plate C. Moreover, the aforesaid slot I also provides for a more eflicient Welding of the wedge member I'I to the rib I3 by reason of the fillet of weld metal W accruing as a result of a Welded tongue-and-groove joint. For a like reason, the marginal edges defining the slot IIzf, on the exterior face of the thrust plate T, are bevelled, as shown in Figs. 6 and 1, whereby a weld metal deposit WI, may be effected later 'in a` welding operation to intimately secure the connecting wedge member I'I in the open slot I6 and to the thrust plate T.y The weld W .is made before .assembling 'th plates ".I' and .C to one another., 'while 'theweld Wl yi's'm'ade after assembling the plates." Obviously, `'the 4.aforesaid tongue-and'- groove joint ,mayA be utilized Vin other manners and anywhere in the mechanical connection between the respective camber and Ythrust plates and Vsuch a connection may be formed in part at least Yby members other than the metal memberl ormenibeis 'herein described.

\ After the blank mates have been formed, the camber plate C and ,the thrust plate" T are brought to nished formfb'y" subjecting each of the partially completed propellerlplates to suitablefmilling', blanking and blade forming operf ations; -the convex conliguration and the pitch being imparted thereto during the operation last noted all aslgenerallyreierred to in the aforesaid pending application'. Thereafter; the aforesaid shallow opening of the camber plate C `is closed 'by the thrust plate T rand the said plates are se.- lired together by'weld'metal W2, with thel taperedgussetlor wedgemember I'I secured to and between said ribs by Welds Wand WI,` as shown 'in4 Figs. 6fand`7, to form the reinforced hollow PEODcllerbladeB.

"In Ythe form of the. invention herein shown, the rib.` .I3 terminates short -of the tapered end of the cainloer plate C .a distance dand the rib I4 terminates short .of the .tapered end vof the thrust Plate YT aV distance dl.. "Further, when the two plates C and T are properly assembled to form the propeller blade, facing surfaces of the ribs I3 ao, I 4 are. engagement with each other or substantially 'so throughout a distance d2, Fig. 5. 'Stillfurthcn when-.the two platesC and T are asSULbEd as described immediately above, fao# ing surfaces of said ribs I 3 and `I 4.are spaced from each .other in a "progressively increasing manner from left to yright throughout .a distance d3, Fig. 5l In accoidne Withgthe invention and for a reason hereinafter to bs described, material is removed in a` suitable manner from the thick end of each rib I3 and I4 to a length asindicated by the distance d2., Vfor example, this vbeing done prior to the .time the platesC and T are assem bled'as described'above.

` ,In accordance with the invention, there is .disposed in the space between the facing surfaces of the ribs lf3 and IA, a connecting or reinforcing metallic wedge mernbengusset or. section of metal I "l', jlfigs. "5I 6 and 7., which is. ,of suitable tapered 4comiguration so that. it Vwill span the space be-v time@ hefacing surfaces of, 'the ribs Iii and I4 einer entirely or 1sie''uwPourv what the. or

t,lates C and T are assembled in blade forming relation. Ordinarily, the connecting member I1 is separately formed although, in a broader concept of the invention, the said member I 'I may be constituted by weld metal, for example, which may be built up between the ribs I3 and I4 by a suitable welding operation.

In a preferred form .of the invention, the connecting wedge member .I'I is denitely located in a predetermined position with respect to the ribs .L3 and It by means of the groove, closed slot, or channel I5 iorrned in the rib I3. 'With `the*connecting wedge member I'I so located, it is seuredor joined to the rib I3 in any llgfblo manner, .for example, by a welded or brazed joint. .formed at the engaging or adjacent msurfaces of said rib I3 and connecting member I'I, this `form of'joint being produced in any suitable manner, as by metallic are, resistance, atomic hydrogen welding, or brazing.

Thereupon the thrust plate T vis. .assembled in proper `.relatif n with 'the camber plate lC and wedge member `I1 as'illustrated .in Fgsj, Gand il. As result, the opposite @dsc surface of th wedge. member `Il is kbrought into 'the opeuslot I5 in the thrust plate T and thus into cngge merit with the rib I 'L `B ey'rond the smallest end tithe aforesaid wedge .member Il, the ribs' I3 .and I Q are `caused to 'engage .each other or. to be closely adjacent each other as here'nbefore men tioncd and clearly shown in Fig; 5.. Accordingly, the thrust, .plate T by .moans of the slotted rib I4, is suitably .securec l,` as by a welding of .equivalent operation, .to those surfaces'ojf the connecting Wedge'mernberfll and the surfaces de nng the ,slot I Q which it faces and projects into. To the form -of the invention shown, although not necessarily, a welded or .brazen joint is'iorrrjied between the aforesaid rib I4 vand the wedge member I'I, by a .suitable Weld- Ving or bra'zingoperation, a welded or brazed joint being also formed ,between the terminal end portionslof the ribs I3 and I4 at the right of the aforesaid member III,`,1iig. .5,- tosecure said rib portionsv directly together throughout the dise tance d2.

"In the alternative arrangement illustrated in Fig. 8, the thrust plate'T is provided with a rib 14:@ having a closedV slot Iiirl formed therein instead of thcopen slot Iii, shown in Fig. 6.

ln'this arrangement, the rib connecting mem, bei' II is positioned in the respective rib slots with writable shim of. .1 uouforv tueuse, lfer exemple, between the surfaces definngsaid slots and the tapering .edges .Qf .the member :IT throughout the length thereof. The blade formi-ng plates `v(l and T are subsequently welded along the marginal coges thereof; .known manner. Thereafter, the blade subjected tothe usual heat treating operations and it is during such heat treatment that the Copper vshim orv linings in each of the slots |50: fuses and brazes the connecting lmember Il in the slots I5@ whereby the plates are joined-between. 1lle .marginal edges thereof as will be lundcrstoou.

As understood vin the art ofproducing a hollow propeller blade from a, pair of facing plat-,esas hereinbefore referred to the inner facing plate surfaces., the area adjacent the tip of the blade are closely spaced. This spacing is so close that there. would 'be interference between `the ribs in said blade tiparea were it not for. the fact that the. rrnaterial defining a tapering rib surface is remoyed throughout the- .distance d2, Fig. 5. Therefore, in V,order torpermit proper: assembly' of the plates C and T, the material defining said tapered rib sections in the region indicated at d2, is removed as aforesaid.

The operations described above result in the production of a hollow propeller blade B, Wherein the thrust plate T is secured to the camber plate C and wherein the reinforcing structure comprising the ribs I3 and I4 together With the connecting wedge member I1 is operatively related to the two plates C and T to reinforce them.

The blade reinforcement comprising the ribs I3 and I4 together with the connecting member I1 increases the stiness of the propeller forming plates with resultant decrease in the amplitude of plate vibration or deflection which may be excited aerodynamically or by engine pulsations. As a result, stresses within the said plates are reduced. Further, such increase in stiffness of the aforesaid plates raises the natural frequency thereof above the range of objectionable frequencies to some extent at least and this decreases the amplitude of plate vibration or deflection.

With respect to a propeller blade wherein the interior chamber is sealed, deformation of the airfoil surface may arise due to the difference of aerostatic pressures exteriorly and interiorly of the blade, this being caused (1) by pressure differences resulting from changes in altitude and (2) by pressure differences due to centrifugal action on the air in the interior blade chamber. The aforesaid blade reinforcement comprising the ribs I3 and I4 together with the wedge member I1 decreases this deformation of the airfoil surface.

Entirely independently of the wedge member I1 and the direct connection between the ribs I3 and I4 near the tip end of the blade, it will be understood that these ribs serve to stiffen the plates C and T in a desired manner. Further, each of said ribs I3 and I4 together with their respective fillets f serve in a highly advantageous manner as a base or extended support to which the connecting wedge member I1 is secured in the closed slot I5 and to the rib I3 of the camber plate C.

It shall be understood that the invention is applicable to various forms or types of hollow propeller blades and that it is not to be restricted to a propeller blade formed from two complementary plates. Thus, the plates referred to in the claims may be formed from a single piece of material. They need not be separate plates secured together in a suitable manner, for example, at their edges as described.

While the invention has been described with respect to a certain particular preferred example which gives satisfactory results, it will be understood by` those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing `from the spirit and scope of the invention and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent, is:

1. In a hollow metallic propeller blade, the combination with a pair of longitudinally tapered plates comprising a camber plate and a thrust plate disposed in facing relation and forming an interior chamber, of a longitudinally disposed rib integral with each of said plates, one of said ribs having an elongated channel formed lengthwise therein short of one end thereof, the other of said ribs having an elongated slot formed lengthwise therein short of one end thereof, and

a wedge-shape connecting member bridging said ribs with its opposite margins disposed and welded in said channel and slot respectively, the remaining portion of each of said ribs beyond said member presenting plane parallel surfaces disposed along the neutral axis of said blade and welded together in direct contacting relation.

2. In a hollow metallic propeller blade, the combination with a pair of longitudinally tapered complementary plates comprising a camber plate and a thrust plate disposed in facing relation and forming an interior chamber, of a central longitudinally disposed rib integral with each of said plates, one of said ribs having an elongated channel therein short of one end thereof, the other of said ribs having an elongated aperture therein short of one end thereof, said ribs being disposed in a single plane and of constant height throughout the channeled and apertured portions thereof, and a tapered connecting member disposed in and bridging the space between said channeled and apertured portions and bonded therein in torque and groove relation, the remaining end portion of each of said ribs presenting parallel surfaces bonded together in direct contacting relation and disposed along the axial center of said blade.

3. In a hollow metallic propeller blade, the combination with a pair of longitudinally tapered plates comprising a camber plate and a thrust plate disposed in facing relation and forming an interior chamber, of a longitudinally disposed rib integral with each of said plates, one of said ribs having an elongated channel formed lengthwise therein, the other of said ribs having an elongated slot formed lengthwise therein, and a Wedge shaped connecting member bridging said ribs with opposite edges disposed and welded in said channel and slot respectively. r

4. In a hollow metallic propeller blade, the combination with a pair of longitudinally tapered plates comprising a camber plate and a thrust plate disposed in facing relation and forming an interior chamber, of a longitudinally disposed rib integral with each of said plates, one of said ribs having an elongated channel formed lengthwise therein, the other of said ribs having an elongated slot formed lengthwise therein, and a Wedge shaped connecting member bridging said ribs with opposite edges disposed and welded in said channel and slot respectively, the weld at said channeled rib lying wholly within said blade, and the Weld at said slotted rib extending from the edge of said connecting member through said slot to the blade surface.

JAMES H. MCKEE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,214,339 McKee Sept. 10, 1940 2,163,209 Pungel June 20, 1939 2,015,332 Baumann Sept. 24, 1935 2,231,888 Couch Feb. 18, 1941 FOREIGN PATENTS Number Country Date 435,630 Great Britain Sept. 25, 1935 134,131 Austria Mar. 15, 1933 343.170 Italy v Sept. 16, 1936 

